A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section, combustion section, and turbine section together define a core air flowpath therethrough. In particular configurations, the turbine section is mechanically coupled to the compressor section by one or more shafts extending along an axial direction of the gas turbine engine.
The fan includes a plurality of blades having a radius larger than the core of the gas turbine engine. The fan and plurality of blades may also be mechanically coupled to one of the one or more shafts such that they rotate along with the turbine. Rotation of the plurality of blades generates thrust for the gas turbine engine and provides airflow to the compressor section of the core.
For at least some gas turbine engines, the fan is a variable pitch fan. It can be desirable to vary a pitch of the fan blades by rotating the blades about respective pitch axes to further increase performance of the gas turbine engine. For example, a primary reason for changing blade pitch is to adjust the blade's angle of attack for optimal performance based on the present air speed of the aircraft and power level of the engine. Alternatively, the pitch of fan blades may be used to reverse the airflow, bypassing the core of the engine, thus providing reverse thrust to aerodynamically brake a landing aircraft.
An actuation member is typically provided in operable communication with the plurality of fan blades to change the pitch of the plurality of fan blades. More particularly, the actuation member includes an actuator packaged within the fan section, typically proximate the plurality of fan blades to rotate the plurality of fan blades about respective pitch axes. However, such a configuration may make it more difficult to repair and/or maintain such actuator. Further, such a configuration may increase the complexity of the engine by, e.g., requiring transfers of pressurized hydraulic fluid from a static frame of reference to a rotating frame of reference.
Accordingly, an actuation member having a more accessible actuator would be useful. Additionally, an actuation member having an actuator for rotating the plurality of fan blades that does not require transferring a pressurized hydraulic fluid from a static frame of reference to a rotating frame of reference would be particularly beneficial.